A problem in utilization of time division multiple access (TDMA) space satellite communication facilities has been to strike an advantageous balance between station costs and network performance; one factor of the latter being the proportionate "throughput" of information bits to non-information bits (e.g. bits used for time control, error control, etc.).
Another problem has been to provide modular time division multiplex (TDM) switching centers for such facilities, which can be conveniently assembled into various station (access node) configurations without precise foreknowledge of station traffic and geographic coverage.
Another problem has been to provide for efficient acquisition, timekeeping and use of satellite time in such networks.
Another problem has been to provide multiple routing capability in modular units relative to a TDMA facility.
Another problem has been to provide efficient terrestrial linkage of a large geographic area to one station (access node) of a TDMA space satellite facility.
Another problem has been to provide for efficient multiplex switching and high speed transmission of diverse digital signal traffic--including telephone (encoded voice), data and non-coded image (NCI) information--by satellite and over point-to-point terrestrial links between physically remote switching centers of one station.
Another need has been to provide digital switching service to voice users of satellites with echo suppression taken care of in the switch.
An object of the present invention is to provide a method of communication fulfilling requirements associated with eliminating the foregoing problems and satisfying respective needs.
Another object is to provide an architecture for modular time domain switching centers, and a related method of communication, which fulfill the foregoing requirements.
Other objects are to provide modular "store and forward" digital switching centers, for operating hierarchically in stations covering a variety of "use-interface" areas relative to access nodes of a TDMA principal trunk facility, and a method of operating a network of such stations.
Another object is to provide a method of TDMA satellite communication characterized by use of digital switching coordinated over all access nodes, time multiplexing and activity compression of switched virtual channels into system transmission channels to achieve station and network efficiencies relative to use of the satellite.
Another object is to provide a method of efficiently switching and handling data and encoded sound (telephone) signals relative to a TDMA link.
A feature is the use of land-linked time and space domain digital switch modules having fixed time capacity to handle a wide range of mixed voice and data traffic in block multiplex relative to a satellite; the extra cost of storage for block handling (over bit handling) being offset by reductions in transmission overhead relative to the land links and the satellite.